Brussels: Turkey raised fears on Wednesday over potential spillover from turmoil in neighbouring Iraq, as NATO promised not to hesitate to defend its ally from the widening conflict.

Speaking on the sidelines of a NATO gathering in Brussels, Turkish Foreign Minister Ahmet Davutoglu called for greater cooperation with its allies to meet the threat posed by the rise of extremist militants in Iraq and the continuing civil war in Syria.

"We are going through a very difficult process in neighbouring regions of Turkey and the Mediterranean and the Middle East," Davutoglu said as he met his US counterpart John Kerry.

"Now it is time to consult more frequently, act together as two strategic allies," he said.

Sunni militants, who have seized a swathe of territory in a lightning offensive in northern Iraq in the past two weeks, are holding 49 Turkish citizens kidnapped from Turkey`s consulate in the Iraqi city of Mosul.

The Islamic State of Iraq and the Levant (ISIL), which Turkey included in its list of terrorist organisations in early June, has also kidnapped 31 Turkish truck drivers.

"I can assure you that NATO allies stand together in solidarity and unity and we are focused on providing effective defence and protection of all our allies including Turkey," NATO chief Anders Fogh Rasmussen said in talks with foreign ministers of the 28-nation alliance.

"We will not hesitate to take the necessary steps to ensure such effective defence protection of Turkey," he added, confirming Ankara had raised concerns about Iraq.

Kerry said at his meeting with Davutoglu that "Turkey is such a key partner in so many ways, but particularly given what is happening in Syria and now in Iraq with ISIL."